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Rhizospheric Soil And Root Endogenous Microbial Community Diversity Analysis On Continuous Cropping Obstacle Of Panax Notoginseng

Posted on:2018-11-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:Y TanFull Text:PDF
GTID:1360330515455971Subject:Environmental Biology
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The dynamic changes in the structure and composition of soil microbial communities are widely used to assess the response of microecosystems.Compared with plant communities,rhizosphere and root endophytic microbiological communities can more sensitively reflect changes in environmental conditions,especially in the early stages of continuous cropping.Notoginseng Radix et Rhizoma is a dry root and rhizome of the Panax notoginseng(Burk.)F.H.Chen.P.notoginseng is negatively affected by continuous cropping and becomes vulnerable to attack by microbial pathogens.There is a serious continuous cropping obstacles,which can not be re-planting less than 8 years.Among them,the diversity of soil microbial community,the types and quantity of soil fungi and pathogens are main reasons that lead to form the continuous cropping obstacles.In the present study,culture-independent Illumina MiSeq was used to investigate the rhizospheric and root endophytic bacteria in response to continuous P.notoginseng cropping practices.The total RNA and DNA were extracted from the 1-,2-,3-year-old notoginseng roots and rhizospheric soil,2-and 6-year fallow soil respectively.The time of planting and abandonment significantly affected the soil bacterial diversity.At the level of DNA,numbers of rhizospheric bacteria decreased with continuous cropping,where as the bacterial diversity in the post-harvest soil samples showing the increased trend,but the bacterial diversity decreased with the abandonment time at the level of RNA.Bacterial composition was affected by the planting and abandonment time.The phyla of Firmicutes and Deinococcus-Thermus were high in RNA level indicated these two phyla were highly active bacteria.In addition,Stenotrophomonas and Pseudomonas were detected as the major genera in both DNA and RNA level.Bacterial diversity was higher in healthy P.notoginseng rhizospheric soils and roots than in those of diseased P.notoginseng,and the genus Candidatus Solibacter and Rhodoplanes are the dominant genera of endophytic bacteria.The soil physical and chemical properties analysis reveals that total phosphorus,organic matter and pH had significant correlation with bacterial community during the continuous P.notoginseng cropping.The occurrence of the disease affects the level of bacterial diversity was demonstrated in this research.The diversity of endophytic bacteria in rhizosphere soil and root of healthy plants was higher than that of root rot at the DNA level,while the bacterial diversity of root rot was the highest at the RNA level.Stenotrophomonas and Pseudomonas showed a high proportions of diversity with root rot sample at the level of DNA and RNA level indicates that Stenotrophomonas and Pseudomonas obviously related to pathogenic bacteria.Culture-independent Illumina MiSeq was also used to investigate the rhizospheric and root endophytic fungi in response to continuous P.notoginseng cropping practices.The results showed that fungal diversity is increased inside the roots and in rhizospheric.Ascomycota,Zygomycota,Basidiomycota and Chytridiomycota were the dominant phyla detected during the continuous cropping of P.notoginseng.The genera of Emericella,Fusarium,and Plectosphaerella were predominantly distributed during continuous cropping.Meanwhile,the soil pH and organic matter had the greatest effect on fungal community composition and diversity.The fungal diversity in the rhizospheric soil and roots of root-rot P.notoginseng plants are less than that of healthy plants in the same cultivating year,thus showing that root-rot disease also affects the community structure and diversity of rhizospheric and root endophytic fungi.At the same time,the diversity of rhizosphere and root endophytic fungi in root rot-diseased plant decreased with the cultivation time.Cylindrocarpon,Fusarium,and Mycocentrospora showed a relatively high proportion of rhizosphere and root of root rot-diseased plant,suggesting that those were might be the potential pathogenic fungus.Furthermore,we detected the the dynamic changes and the correlation relation with the soil environmental factor of five possible pathogens:Stenotrophomonas,Pseudomonas,Cylindrocarpon,Fusarium and Mycocentrospora.The results showed that the selected pathogens are the dominant distribution in rhizosphere soil of root rot-diseased plant.The genera of Fusarium,Mycocentrospora and Cylindrocarpon showed an increasing trend in 3-year-old root rot-diseased notoginseng root endophytes,which indicated that they could be originated from rhizosphere soil to root.Correlation analysis showed that there was a significant negative correlation between soil organic matter and Pseudomonas.Neverless,there is a significant positive correlation between soil available potassium and Stenotrophomonas,Mycocentrospora.This is the first report about culture-independent method to analyze the population variation,development and succession of soil microbial communities at the level of endophytic and rhizosphere soils of P.notoginseng continuous cropping.The study will not just help to restore the microbial communities from continous cropping obstacle,but also provide invaluable information to eliminate the continuous cropping abstacles of P.notoginseng.
Keywords/Search Tags:Panax notoginseng, microbial community, continuous cropping obstacle, rhizosphere soil, root endogenous microorganism
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